Pulse generator



J y 29, 1952 G. F. SCHRADER I 2,605,449

PULSE GENERATOR Filed June 5, 1948 D. C VaLrs IN VEN TOR. GEORGE E SCH/MDER ,4 Tram/5y Patented July 29, 1952 PULSE GENERATOR George F.Schrader, Richmond, Califl, assignor to the United States of America asrepresentedby .the United States Atomic Energy Commission ApplicationJune 3, 1948, Serial No. 30,850

5 Claims. (Cl. 315-230) This invention relates to an electronic circuitand more particularly to a pulse generating network for producing pulsesof variable duration.

In general, the type of electronic network proposed comprisescombinations of differentiating circuits, amplifying circuits, clippingcircuits, and multivibrator circuits, which become com" plex instructure and costly to'manufacture. It is proposed by'th-is inventionto provide a pulse generator capable of developing pulses of variableduration using apair of gaseous discharge tubes, the anodes of which areinterconnected with an artificial transmission line section, and thecontrol grids of which are energized by means of resistance-capacitanceintegrating circuits.

It is thereforev an objectoi this invention to provide a new andimproved pulse generating circuit.

Anotherobject of the invention is to provide a simplified and lesscostly pulse generatingcircuit.

Still another object .of'the invention is to provide a pulsegeneratingcircuit capableof producing pulsesof variable duration which canbecontrolledbya single variable element .over a substantially. largerange. V

A further object of .the invention is to provide a pair'of gaseousdischarge tubes controlled to discharge asectionof artificialtransmission line and adapted to provide a pulse of variable duration inresponse to an inputpulse.

Other objects andadvantages will be apparentin the following descriptionand claims considered together with theraccompanyingdrawing in which thefigure is a schematic wiring diagram embodying the "invention and is thesole drawing thereof,

Referring to the drawing. inrdetail, there is showna potentiometerw IIhaving its variable connection I2 connected to an external source ofsquare waves of voltage. One end I3 of the potentiometer II isconnected'to ground through a condenser! and the other end I6 isconnected tolground through another condenser I1. The

potentiometer end I3 is connectedto the control I8 is connected to thecontrol grid of asecond triode gaseous discharge tube =21 through acoupling condenser 28. The control grid of this tube 21 is furtherconnected to the negative voltage source 2| through a resistor 29. Otherconnections of the tube 21 are as follows: the cathode is connected toground through a resistor 3I and the anode is connected to one end of anartificial transmission line 32 comprising an inductance 33, and twocondensers 34 and 33. The other end of the transmission line 32 isconnected to the anode of the tube I8. The con denser 34 is connectedfrom one side of the inductance 33 to ground and the condenser 36 isconnected from the other side of the inductance 33 to ground; An outputlead 31 is connected to the cathode of the tube 21 and serves as asource of output voltage for the circuit.

Now consider the operation of the invention with the sources ofunidirectional voltages 2i and 24 suitably energized and with a squarewave of voltage impressed at the adjustable element I2 of thepotentiometer II. For proper operation of the circuit, the inductanceandcapacitance of the artificial transmission line 32 are chosen so thatthe traveling wave time thereof is equal to the duration of the inputsquare wave of voltage and the values of the cathode resistors 23 and 3Iof the tubes I3 and 21, respectively, are so chosen as to be equal tothe characteristic resistance of the artificial transmission line 32.The values of these elements can be calculated readily by usingwell-known transmission line formulas; that is, the traveling wave timeis-equal to the square root of the product of the inductance 33 andcapacitance 34 and 36 of the artificial transmission line 32 and thecharacteristic resistance of the line 32 is equal to the square root ofthe quotient of the inductance 33 divided by the capacitance 34 and 36.With the above conditions satisfied and the adjustable element I2.of thepotentiometer II positioned near the potentiometer. end I3, thecombination of the capacitance. of the condenser. I4 and the resistanceoi the potentiometer II forms an integrating network for theinput squarewave of voltage. The same occurs at the end I6 of. the potentiometer IIin conjunction with the condenser I1. Thus, it is seen that sawtoothwaves of voltages are coupled to the control grids of the two tubes I8and 21 by the condensers I3 and 23 respectively. Since the adjustablearm of the potentiometer is, in this instance, positioned near the endI3 thereof, the slope of the sawtooth wave at the control grid of thetube I8 will be greater than that at the control grid of the tube 21 andthe firing voltage of the tube I 8 will be reached'soo'ner'than that ofthe tube 21.

During the time both of the tubes I8 and 21 are nonconducting, theartificial transmission line 32 becomes charged to a voltage equal tothe positive voltage of the source 24 through the resistor 26 which hasa high value in comparison with the characteristic resistance of theline 32. Now, with the adjustable element I2 of the potentiometer IIpositioned as stated above, the tube I8 conducts soon after theoccurrence of a square wave of voltage at the input and the voltage ofthe line 32 falls to one-half of its original value with a negativevoltage wave equal to onehalf the original value travels down the line.32 toward the tube 21. If the voltage at the control grid of the tube 21never becomes sufficiently positive to fire the tube 21, the travelingwave, after the time determined by the inductance and capacitance of theline 32 as described previously, is reflected in such a manner that theanode voltageof the tube 21 becomes zero. Then after a time equivalentto the travel time computed above, the anode voltage of the tube I8becomes zero and the tube I8 ceases to conduct. Under this circumstancethe tube 21 does not conduct, therefore there can be no voltagedeveloped across the resistor 3| and the output voltage of the circuitis zero.

Under the same circumstances as outlined above, but with the adjustableelement I2 positioned sufiiciently toward the end I6 of thepotentiometer II that the tube 21 becomes conductive prior to thereflection of the traveling wave caused by the earlier conduction of thetube I8, a second traveling wave of voltage of equal magnitude isdeveloped traveling in the oppositedirection. The tube 21 then continuesof the line 32. This occurs in a manner analogous to the first conditiondiscussed above; that is, the tube 21 conducts during the time it takesfor the traveling wave of voltage to go from one end of the line 32 tothe other and be reflected back.

From the foregoing it is seen that a square wave voltage input can beutilized by this circuit to generate an output pulse of voltage ofvariable duration between zero and twice the traveling wave time for theartificial transmission line.

vlNhile the salient features of this invention have been described indetail with respect to one to conduct until the time when the firsttraveling reaches the end of the line 32 nearest the tube 21, at, whichtime the anode voltage of the tube 21 drops to zero. Thus, there is apositive voltage developed across the resistor 3| from the time the tube21 starts .to conduct until the anode voltage of the tube becomes zeroand the tube is cut off. V

Now, with the adjustable element I2 of the potentiometer II positionedat the center of the potentiometer, sawtooth voltages of equal slope andmagnitude areimpressed at the control grids of the tubes I8 and 21. Itcan be seen from this and the foregoing that both of the tubes I8 and 21will thus start toconcluct at the same time sending 'a negative wave ofvoltage traveling across the line 32 from each end. The tubes willconduct for the time determined by the inductance and capacitance of theline 32, and will be simultaneously out off when the line is dischargedand an output voltage during this time will be developed. at the outputlead 31.

If thev adjustable element I2 of the potenti- 'ometer. I I is moved fromthe center position to a position nearer the. end I6 of thepotentiometer, thetube-21 willconduct first, having the sawtooth voltageof greater-slope impressed at the control grid. In-thissequence ofoperation,

which is analogous to that described above, traveling waves are startedacross the line 32 to discharge the line and cut off the tubes I8 and21. V In this instance the tube 21 conducts from the time itscontrolgrid becomes sufliciently positive until-a time, determined by theinductance and capacitance of the line 32, later.

Now, with the adjustable element I2 of the potentiometer II very nearthe end I6 of the potentiometen'the tube -21 will conduct for a periodtwice as long as the traveling wave time embodiment it will, of course,be apparent that numerous modifications may be made within the spiritand scope of the invention and it is therefore not desired to limit theinvention to the exact details shown except insofar as they may bedefined in the following claims.

What is claimed is: 7 I

1. In an electronic circuit of the class described, the combinationcomprising a pair of gaseous discharge tubes having at least a cathode,a control grid, and an anode, a resistor connected in the cathodecircuit of each of said tubes an artificialtransmission line connectedbetween said anodes for storing energy, a pair ofresistance-capacitance, integrating networks having a common variableinput connection and separate outputs, the control grid of each of saidtubes being connected to the output of one of said integrating networks,and means for charging said line, whereby the conduction of said tubesis controlled to discharge said line in response to a square wave ofvoltage at said input connection and to produce an output voltage ofvariable duration at one of said cathodes.

2. In an electronic circuit of the class described, the combinationcomprising a pair of gaseous discharge tubes having at least a cathode,a control grid, and an anode, an artificial transmission line connectedbetween said anodes for storing energy, a pair of integrating circuitscomprising a potentiometer, and two condensers, one of said condensersbeing connected to each end of said potentiometer, a source of squarewaves of voltage connected to the adjustable element of saidpotentiometer, one of said integrating circuits being connected to eachof said control grids for controlling the operation of said tubes inresponse to said input voltage and the position of said variableelement, and means, for charging said line, whereby output voltages ofvariable duration are produced at one of said cathodes.

3. In an electronic circuit of the class described, thecombinationcomprising an input and an output, a pair of variable integratingcircuits having a common connection to said input, a pair of gaseousdischarge tubes having at least a cathode, a control grid, and an anode,one of said control grids connected to each of said integratingcircuits, an artificial transmission line connected between said anodes,and means for charging said line, one of said cathodesbeing connected tosaid output.

4. In an electronic circuit for'producing rectangular voltages havingvariable duration, the combination comprising a source of rectangularvoltages, a potentiometer having its adjustable element connected tosaid source, a separate condenser connected between each end of 'saidpotentiometer and ground forming a pair of inrating circuits, wherebythe voltage developed across each of said condensers is a triangularwave having a maximum voltage which is variable by the adjustableelement of said potentiometer, a first and second gaseous dischargetubes having a cathode, a control grid, and an anode, means connected tosaid control grids for normally biasing said tubes beyond cut-off, meansfor coupling the voltage across said condensers to the control grids ofsaid tubes, 2, section of artificial transmission line connected betweenthe anodes of said tubes, charging means connected jointly to the anodeof said first tube and to one end of said artificial transmission line,and an output connection connected to the cathode of said second tube.

5. In an electronic circuit of the class described, the combinationcomprising a potenti v ometer having an adjustable element serving as aninput connection for square waves of voltage, a first condenserconnected between one end of said potentiometer and ground, a secondcondenser connected between the other end of said potentiometer andground, a first gaseous triode tube having the cathode thereof connectedto a resistor which is in turn connected to ground, a first couplingcondenser connected between the control grid of said first tube and thejunction of said potentiometer and said first condenser, means alsoconnected to the control grid of said first tube for biasing the tubebeyond cut-ofi, a dropping resistor connected to the anode of said firsttube and serving as a connection for a positive unidirectional operatingvoltage, a second gaseous triode tube havingthe cathode thereofconnected to a resistor which is in turn connected to ground, a secondcoupling condenser connected between the control grid of said secondtube and the junction between said potentiometer and said secondcondenser, means also connected to the control grid of said second tubeREFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name 7 Date 2,197,414 Place Apr. 16, 19402,301,195 Bradford Nov. 10, 1942 2,301,220 Lowe Nov. 10, 1942 2,409,897Rado Oct. 22, 1946 2,445,888 Rado July 27, 1948 2,446,838 Lawrence, JrAug. 10, 1948 2,458,574 Dow Jan. 11, 1949 2,496,543 Kanner Feb. 7. 1950

